钢管混凝土框架-屈曲约束支撑结构概率地震易损性评估研究

Probabilistic Seismic Fragility Evaluation of CFST Frames with Buckling-Restrained Braces

为了研究钢管混凝土(CFST)框架-屈曲约束支撑(BRB)结构的抗震性能以及地震动持时对结构概率地震易损性的影响,基于能量平衡的塑性设计方法,设计了9层框架支撑结构.选取其中一榀单层单跨的框架支撑试件进行了低周循环加载试验和数值分析.采用OpenSees程序建立了9层典型三跨子结构的弹塑性分析模型;通过增量动力分析法得到了结构在不同工程需求参数和地震动强度参数下的易损性曲线,分析了地震动持时对结构抗震性能的影响.研究结果表明:试件的水平荷载-位移滞回曲线饱满,耗能稳定;结构90%的塑性变形耗能集中于屈曲约束支撑;整体损伤因子(ODI)可以较好地反映地震动持时对框架支撑结构累积损伤的影响;长持时地震动下结构的倒塌中位值比短持时的低24%.以ODI为工程需求参数时,考虑地震动谱加速度和重要持时的地震动强度综合指标INP-D表现出更优的实用性、有效性、充分性和调幅鲁棒性.对于I_(NP-D),罕遇地震水平下,长持时地震动下的ODI超越0.2和0.4限值的概率分别是短持时的1.74和5.0倍,因此建议钢管混凝土框架-屈曲约束支撑结构的抗震设计和分析应关注地震动持时对结构累积损伤的影响.

A nine-story structure was designed based on a plastic design method using energy balance to investigate the seismic behavior and the influence of ground motion duration on the probabilistic seismic fragility for the concretefilled steel tube(CFST)frames with buckling-restrained braces(BRBs).Low cyclic testing and numerical analysis were performed on a one-bay one-story braced frame specimen.The elastic-plastic analytical model of the nine-story typical three-span substructure was established using the OpenSees program.The effect of ground motion duration on the seismic intensity performance of the structure was analyzed via fragility curves using various engineering demand parameters(EDPs)and intensity measures obtained from incremental dynamic analysis.The analysis results showed that the hysteretic curve of the test specimen is plump and stable.BRBs dissipated 90%of the hysteretic energy of the structure.Meanwhile,the overall damage index(ODI)could better reflect the influence of the ground motion duration on the cumulative damage effect of the structure.Long-duration ground motions reduced the median value of struc-tural collapse by 24% compared to short-duration ground motions.With ODI as the EDP,the combined index I_(NP-D),which considers spectrum acceleration and a significant duration,shows excellent practicability,efficiency,sufficiency,and scaling robustness.For the INP-D,the probabilities of ODI exceeding 0.2 and 0.4 under long-duration ground motion were 1.74 and 5.0 times that under a short-duration ground motion,respectively,for the structure subjected to rare earthquakes.Therefore,the influence of ground motion duration on the cumulative damage for CFST frames with BRBs should be considered during structural seismic design and analysis.